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What Is Melatonin?

Last updated Nov. 10, 2016

Approved by: Krish Tangella MD, MBA, FCAP

Melatonin is a hormone found in humans that is produced in the area of the brain called the pineal gland. This gland is located in the center of the brain. Some adults take melatonin supplements to help with their sleep. Some supplement users have claimed to have increased and intense dreaming.


Melatonin is a hormone found in humans that is produced in the area of the brain called the pineal gland. This gland is located in the center of the brain. The hormone signal is part of a system that controls the sleep-wake cycle by causing drowsiness and lowering the core body temperature.

The production of human melatonin decreases with age. Babies begin to produce melatonin after around the third month following birth. In teenagers, the release of melatonin is delayed, which causes them to have late sleeping and waking times. Studies have suggested that delaying school ‘start times’ for teenagers could help improve grades because teenagers naturally sleep late.

What type of light affects melatonin?

Melatonin hormone levels vary throughout the day. It is released in the brain at night or dark; the release is inhibited by light, or during the day. Blue light, in particular, inhibits the production of melatonin. Some studies suggest wearing glasses that block blue light in order to help promote sleepiness in humans.

Melatonin benefits:

Melatonin plays a particular role in protecting the DNA (the body’s blueprint) by acting as an antioxidant. An antioxidant scavenges harmful biological wastes that can be harmful to the cell. The harmful biological wastes, called free radicals, can potentially cause cancer by mutating the DNA. When not working by itself, melatonin works with other antioxidants and has proven to be twice as effective as vitamin E when it comes to protecting cells in the body. 

Though the pathway remains unclear, melatonin interacts with the immune system, acting as an anti-inflammatory. An anti-inflammatory reduces swelling or redness within the body that is caused by harmful stimuli. Studies are still being conducted to ascertain the overall effectiveness of melatonin.

Melatonin and sleep:

Some adults take melatonin supplements to help with their sleep. Some supplement users have claimed to have increased and intense dreaming. Studies have shown that high doses of melatonin drastically increased the amount of REM sleep and dream activity in individuals with and without narcolepsy.

A study published in The Lancet in 1995 found that elderly people, regardless of their health status, needed less time to fall asleep and wake up when given two milligrams of melatonin. The researchers suggested that melatonin supplementation could increase the ability to sleep in elderly individuals.

A study published in Sleep in 1997 studied healthy males with an average age of 26 years. It was found that the male participants who took melatonin fell asleep approximately 40 minutes sooner than the male participants who did not take melatonin supplements. The dosage amount appeared to have no role to play, as long as it was taken approximately an hour before bedtime. 

Studies have demonstrated that the use of melatonin can be effective in children with autism and for teens with “night owl syndrome”. On the other hand, the National Institutes of Health warns that melatonin supplements should not be used by children because it may be unsafe and impact their growth and development. 

Melatonin has also been shown to help individuals fight certain types of cancer. Studies have demonstrated that men with lower melatonin levels have been linked with prostate cancer. Melatonin is seen to block the growth of prostate cancer cells. Laboratory experiments have found that low levels of melatonin stimulate the growth of certain types of breast cancer cells, whereas adding melatonin to these cells appears to slow their growth.

It is always recommended to seek advice of a healthcare professional before adding to or adjusting your sleep routine with melatonin, as he or she can help you decide if melatonin supplements are right for you, what the proper dosage would be, and if the benefits of supplementation outweigh the melatonin side effects. Nevertheless, for individuals who would like to consume melatonin naturally, bananas, pineapples, and oranges are wonderful selections to choose from.

Additional Resources:

Carrillo-Vico, A., Guerrero, J. M., Lardone, P. J., & Reiter, R. J. (2005). A review of the multiple actions of melatonin on the immune system. Endocrine, 27(2), 189-200.

Challet, E. (2007). Minireview: entrainment of the suprachiasmatic clockwork in diurnal and nocturnal mammals. Endocrinology, 148(12), 5648-5655.

Garfinkel, D., Laudon, M., Nof, D., & Zisapel, N. (1995). Improvement of sleep quality in elderly people by controlled-release melatonin. The Lancet,346(8974), 541-544.

Hardeland, R. (2005). Atioxidative protection by melatonin. Endocrine, 27(2), 119-130.

Kayumov, L., Casper, R. F., Hawa, R. J., Perelman, B., Chung, S. A., Sokalsky, S., & Shapiro, C. M. (2005). Blocking low-wavelength light prevents nocturnal melatonin suppression with no adverse effect on performance during simulated shift work. The Journal of Clinical Endocrinology & Metabolism, 90(5), 2755-2761.

Kunz, D., Mahlberg, R., Müller, C., Tilmann, A., & Bes, F. (2004). Melatonin in patients with reduced REM sleep duration: two randomized controlled trials. The Journal of Clinical Endocrinology & Metabolism, 89(1), 128-134.Lemus-Wilson, A., Kelly, P. A., & Blask, D. E. (1995). Melatonin blocks the stimulatory effects of prolactin on human breast cancer cell growth in culture.British journal of cancer, 72(6), 1435.

Navara, K. J., & Nelson, R. J. (2007). The dark side of light at night: physiological, epidemiological, and ecological consequences. Journal of pineal research, 43(3), 215-224.

Pohanka, M. (2013). Impact of melatonin on immunity: a review. Central European Journal of Medicine, 8(4), 369-376.

Reiter, R. J. (1991). Pineal Melatonin: Cell Biology of Its Synthesis and of Its Physiological Interactions. Endocrine reviews, 12(2), 151-180.

Reiter, R. J., ACUÑA‐CASTROVIEJO, D. A. R. I. O., TAN, D. X., & Burkhardt, S. (2001). Free Radical‐Mediated Molecular Damage. Annals of the New York Academy of Sciences, 939(1), 200-215.

Zhdanova, I. V., Lynch, H. J., & Wurtman, R. J. (1997). Melatonin: a sleep-promoting hormone. SLEEP-NEW YORK-, 20, 899-907.

Helpful Peer-Reviewed Medical Articles:

Paradies, G., Petrosillo, G., Paradies, V., Reiter, R. J., & Ruggiero, F. M. (2010). Melatonin, cardiolipin and mitochondrial bioenergetics in health and disease. Journal of pineal research, 48(4), 297-310.

Smits, M. G., van der HEIJDEN, K. R. I. S. T. I. A. A. N., MEIJER, A. M., COENEN, A. M., & KERKHOF, G. A. (2003). Melatonin improves health status and sleep in children with idiopathic chronic sleep-onset insomnia: a randomized placebo-controlled trial. Journal of the American Academy of Child & Adolescent Psychiatry, 42(11), 1286-1293.

Acuna Castroviejo, D., C Lopez, L., Escames, G., Lopez, A., A Garcia, J., & J Reiter, R. (2011). Melatonin-mitochondria interplay in health and disease.Current topics in medicinal chemistry, 11(2), 221-240.

Reiter, R. J., Tan, D. X., Mayo, J. C., Sainz, R. M., & Lopez-Burillo, S. (2002). Melatonin, longevity and health in the aged: an assessment. Free radical research, 36(12), 1323-1329.

Bliwise, D. L., & Ansari, F. P. (2007). Insomnia associated with valerian and melatonin usage in the 2002 National Health Interview Survey. SLEEP-NEW YORK THEN WESTCHESTER-, 30(7), 881.

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Nov. 10, 2016
Last updated: Nov. 10, 2016